Latvian WtE nest webcamera Juras-erglis: Discussions

White-tailed eagles in Latvia

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ame
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Re: Latvian WtE nest webcamera Juras-erglis: Discussions

Post by ame »

Liz, there is no suitable place for discussion like this, not even in the Social corner. :slap:

Sonchik! :hi:
there certainly was a third eagle in the forest. this eagle flew by the nest out of our sight but Milda and Mr X saw him/her. their behaviour clearly indicated that they were looking at a third eagle. the eagle didn't say anything either so we can't know whether it was a male or a female.
- i didn't find a fight there on April 1st though. :puzzled:

and yes, it was so ridiculous to see so many eagles who looked so much alike. besides many of them had tails which looked so much like Milda's tail. :mrgreen:
i'll try to find clear pictures of their beaks, but i'll do that later.
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Post by Ajeta »

Sonchik wrote: January 2nd, 2022, 8:26 am
Nice picture. At first sight I would be tempted to think it might be Mr L. As I have committed this mistake once before, though (confuse Mr L with this eagle), I shall refrain from it here. I believe it is Mr X, the eagle much around in the first days of April, with whom Milda seemed to feel rather comfortable. He and Mr L have some likeness at first glance, but also great differences. Mr L is bigger and stronger, has a different beak, and his wings are overall of darker impression, especially the feathers at the bottom of the wing are less dark/light striped, but darker.
(I confused the two on April 6th, in the late afternoon, when Mr L first appeared on the nest. Everybody thought it was a female, he was so massive somehow, but I cheered and thought it was Mr X. I realized shortly afterwards, but am still embarrassed by that faux pas.)
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Post by Ajeta »

The idea brought up by Liz in her last post here that possibly a scar on the beak could help to identify Mr L and especially prove for everyone to see that he is indeed the eagle who first visited the nest on April 6th, 17:23 is very attractive.

Yet is that line indicated by the red arrow actually a scar? Or is it perhaps the rim of that structure which contains the nostrils of the eagle and sits atop the beak, but runs down the sides as well, a little bit like a saddle, and perhaps the shadow it throws on the beak?

Here are three pics which show such lines on beaks, of Silva (from Sliteres, whom Liz mentions for comparison), Mr L. and Milda. But perhaps I missed what was really indicated as scar?

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Post by Ajeta »

Ajeta wrote: January 4th, 2022, 10:09 pm
Just two more pics (both Mr L) on how this structure shows itself at different angles and in different light:

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Post by ame »

i also made a few pictures of the beaks of the eagles.
Mr X
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"Egg-Roller" (i couldn't get as clear picture as Liz although i took all the possible frames)
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Mr W together with Milda.
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Post by ame »

Chips i skipped because he was so unique.
Mr L. here i could pick a clear picture.
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and finally Milda and Raimis.
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Post by ame »

i came to the same conclusion as Ajeta. the "wrinkle" is not a scar, but all eagles have it.

the "wrinkle" in the beak seems to be the border between the cere and the bony beak which is covered b y a layer of keratin.
"Birds from a handful of families—including raptors, owls, skuas, parrots, turkeys and curassows—have a waxy structure called a cere (from the Latin cera, which means "wax") or ceroma which covers the base of their bill. "
https://en.wikipedia.org/wiki/Beak#Cere

in some birds of prey the cere and the beak are different colour. all eagles have this wrinkle. in some pictures it's visible, in some pictures not.
this is the eastern imperial eagle (Aquila heliaca)
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in WTE the colour of the cere is the same as in the rest of the beak.
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Post by Ajeta »

I said I would do some lines and arrows to point to the various spots in Mr L's plumage of his right wing to show that he's - from all that the camera can tell us - probably identical with the eagle of April 6th, 17:23 as well as the one under attack by Mr C on April 7th & 8th. But I remembered this post by Sonchik
https://www.looduskalender.ee/forum/vie ... 86#p795086
where some of it has already been pointed to. According to her post above she doesn't seem to have changed her opinion on that.

To support it further, here a few more pics of his tail, folded and unfolded, on different days during that period, and of it spread out. Light, speed, wind and camera angle have an influence. But the essential features, I think, are visibly very similar. So similar I would hold that the chance to get two or even more eagles with those same features would be rather small. (Though no feature on its own would be proof enough, of course. It's their sum that gives good grounds for this hypothesis.)

1. tail folded
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2. tail spread: in almost all one can discern a "chessboard pattern" in the upper part of the tail (or half, on the 8th of April):
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Whether we had 5, 6 or 7 contenders in spring '21 makes a difference of up to 40%. So it could be statistically relevant. My main concern, however, is Mr L: His truly heroic fight for this kingdom and Queen Milda's hand must be told to the world in full. :laugh:
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Post by Ajeta »

Another mark of Mr L were two gaps in his left wing, one smaller, one bigger.
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The same can be said of the eagle attacking Mr Z on April 5th twice in less than two minutes:

15:33
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In the right of the two pics, he can be seen under the right branch behind a snowflake, but the big gap in the left wing is well visible.
15:34
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Here in both pictures he's "under" Mr Z, ie behind the top branch.

That Mr L was in fact the one battling and fighting Mr Z (before later having to fight Mr C as well), might be supported by a similarity of the voices of Mr L and the opponent of Mr Z as could be heard calling from the forrest.

A beautifully clear sample of Mr L's voice presented by Ame you can find here:
https://www.youtube.com/watch?v=YiOKaJblMVw&t=23s
He's the first to call, and there's little disturbance by any background noises as it is at night.

A good sample for Mr Z's presumed opponents voice on April 5th is the following, presented by Ame, too. Rain, wind, Milda and Mr Z make hearing a bit of a tour de force, but the voice of the caller is quite distinct, too:
https://www.youtube.com/watch?v=YD1TOby0j0A&t=5s
(starting at 12:58:06 with a little chep chep as Mr L occasionally can be heard to do)
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Post by Liz01 »

Molting in big birds can take several years. The flight feather change takes the longest. Gaps caused by molting are not proof to identify a bird. It may be possible to do it if the bird has been seen many times in a short period. But longer than a year, that seems unlikely. The gap would have to be filled even if the feather had failed only last year. so can it be any other eagle? :puzzled:
Of course, that wouldn't fill the gap entirely, but it would be seen. Since all eagles molt, all eagles lose their flight feathers and replace them.
I believe no ornithologist would use molting as evidence?
I would prefer other features.

Allometry of the Duration of Flight Feather Molt in Birds
https://www.looduskalender.ee/forum/vie ... 15#p834115
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Post by Liz01 »

Ajeta wrote: January 4th, 2022, 10:09 pm ....
Yet is that line indicated by the red arrow actually a scar? Or is it perhaps the rim of that structure which contains the nostrils of the eagle and sits atop the beak, but runs down the sides as well, a little bit like a saddle, and perhaps the shadow it throws on the beak?
This scar can only be seen on Silva's left side.

Erik has one too- Eve not!
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Post by Ajeta »

Liz01 wrote: January 10th, 2022, 6:31 am
Thank you very much for that interesting information regarding moulting!

I'm not sure it pertains to the problem in question, for two reasons:
Firstly, the gap might be due to a broken feather rather than one missing bc of moulting?
Secondly, it seems more of a logical problem than an ornithological one.

We had several hitherto unknown male eagles at the nest during approximately one month (end of March '21 - end of April '21).
One of them - later securely identified and named Mr L - was observed to have two gaps in his left wing.
The others didn't (or if they did have gaps, then at least not in the same place).
So that seemed one of the characteristics that possibly distinguished this eagle from the others (during that short time in that confined environment).

Even an ornithologist might well draw the conclusion, I believe, that similar gaps in the left wing might be considered a distinctive characteristic within a small group during a short period. Might - of course it could also be mere coincidence, and that there were indeed two different males with gaps at approximately the same place around the nest last spring. That cannot be excluded. That's why, even as nonornithologist, I would never presume to identify an eagle by this - or indeed almost any - mark alone.
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Post by Ajeta »

Liz01 wrote: January 10th, 2022, 9:31 am This scar can only be seen on Silva's left side.
To me, this looks similar?
But I might still not understand what you mean.
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Post by Ajeta »

Ajeta wrote: January 11th, 2022, 6:29 pm
I was in a hurry here, and would like to explicate a bit.
The question was if moulting would exclude the possibility that Mr L not only drove Chips away (April 27ff), but was also the eagle fighting Mr Z (April 5), as both times gaps in the left wing could be observed in similar places.

In the study Liz posted above, the bearded vulture (gypaetus barbatus) is said to take approx. 90 days for his longest primary.
There's no time given for WTE, but it normally should not take longer than that.
So the replacement of a feather in the wing should have happened within three months, I suppose.
The eagle of April 5, 2021 should then have filled his gap by Mid-July at the latest.
The eagle of April 27, 2021 his gap by the end of July.
Why then has Mr L - who's securely identified in the o-thread as at least the eagle of April 27, 2021 - still got a gap in his left wing?

Perhaps because
- it is the next or even next but one feather in moult causing that gap? It may be difficult to ascertain that on camera; but moulting happens in sets & series, as far as I understood.
- the gap is not caused by moulting?
- the rules of moulting have not been completely understood yet?

There may be other explanations yet. At any rate, all pertain as much to the eagle of April 27, 2021 as to the one of April 5, 2021. Thus it seems moulting would not exclude the possibility that Mr L was indeed both these eagles, on April 5 & April 27.

On 29.4.2021 Mr L presented his wing in such a way that the gap could be seen from the outside as well as from the inside. At that time, if I am not mistaken, it does not seem to have been a primary which caused it, as there seem to be all ten of them there?

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Post by Ajeta »

Grieta wrote: June 6th, 2022, 4:35 pm But I still leave the possibility that it is Voldis if he had lost all the upper feathers of his tail which formed dark spots.
It's not there anymore! :shock:

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I'm replying here in the discussion thread so as not to swamp the o-thread with this topic.
Firstly, I'm not sure I understand you here: Those two pics in your post are from the same stay of the eagle in question, aren't they? So what do you mean to illustrate with those two pics? I'm sorry I'm so slow!

Secondly, I believe the protrusion is still there in the second picture above. I drew a line around it here:

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It only seems shorter, possibly bc it is lifted a bit and the tail lowered - it seems one can almost recognize part of its shadow on the white beneath (in your pic - in mine the line is in the way). Also, if looking closely at the enlarged picture one can discern the end of some dark streaks underneath the protrusion left and right.
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Post by Ajeta »

Here are three pics from ame's video of March 10th, 2022 which I mentioned yesterday (cf my post https://www.looduskalender.ee/forum/vie ... 00#p860500 ), of the feather shuffle at 18:31:30. They show well, I believe, how variable this protrusion (or more than one?) can look as regards position, length, width):

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